Audio-based security system devices such as glassbreak detectors and listen-in devices utilize an audio transducer such as a microphone to sense acoustic waves and process the sensed acoustic waves in accordance with the requirements of the device. For example, a glassbreak detector will sense acoustic waves, process and analyze them to determine if the waves are the result of a glass breakage event, and then notify a control panel accordingly. A listen-in device uses a microphone to pick up sounds in a protected area and either convey those sounds in real time to a central station operator, record the sounds for archival purpose, or both. In either case, the operation of the microphone as an acoustic transducer is critical in the proper functioning of the device.
Thus, intruders may sabotage the microphone in an attempt to disable or render useless the security system device. For example, by destroying a microphone in a glassbreak detector, the intruder will have disabled the alarm capabilities of the detector and thus compromised the area under surveillance by that detector.
One method of sabotage that is tested (for example in European certification test labs) is the puncturing of the microphone diaphragm. In order to ascertain sabotage of the microphone, a visual (mechanical) inspection of the microphone maybe utilized. This may be disadvantageous since it requires the microphone to be inspected. Since sabotage may occur just prior to an intrusion, reliance on periodic visual inspections may not be effective.
Thus, it is desired to provide an automatic manner of detecting if a microphone has been sabotaged such as by damage to the diaphragm.